<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<meta http-equiv="X-UA-Compatible" content="IE=edge">
	<title></title>
	<link rel="stylesheet" href="">
</head>
<body>
<script>
var a= {}
Object.defineProperty(a,"b",{
 value:123
});
//下面是上面的默认代码
Object.defineProperty(a,'b',{
	value : 123,
	writable : false,//不可写，只读
	enumberable : false,//不可枚举
	configurable : false,//总开关，决定这个对象是否可以配置属性
})
console.log(a.b);//123
</script>	
</body>
</html>